Woolley (1) has prepared a number of ethers of N-acetyl-3,5-diiodotyrosine and found them to interfere with various effects of thyroxine on amphibian larvae. Some of Woolley’s observations were confirmed and extended by Winder and Frieden (2) and by Williams et al. (3). It is the purpose of this report to investigate the competitive nature of several thyroxine inhibitors and to determine the st...

Platelet monoamine oxidase (MAO) activity and serum thyroxine indices were determined in 62 children and adolescents currently undergoing medical treatment for various thyroid disorders. The platelet MAO activity of these patients was similar to that of control and contrast groups previously reported, and there were no differences when patients were grouped according to specific thyroid disorde...

Although biological methods are used for assessing the value of thyro-active materials, chemical methods are also available to determine the thyroxine content of such substances. These methods are mainly based on the estimation of iodine as 'thyroxine iodine' (Harington & Randall, 1929; Leland & Foster, 1932; Brand & Kassell, 1939). Polarographic analysis suggests itself as a means of simplifyi...

In the course of a search for compounds which might prove to be competitive inhibitors of thyroxine in its action on the peripheral tissues, we have initiated a study of the relationship between chemical structure and thyroxine-like activity of a number of thyroxine analogues. Early attempts to relate chemical constitution to physiological activity have been summarized by Harington (1, 2) who c...

Hypothyroidism There is general agreement that all patients with symptomatic hypothyroidism should receive replacement treatment. MANAGEMENT Thyroxine should be used in the routine management of hypothyroidism. The initial dose should not exceed 0-05 mg daily in patients over 40; an initial dose of 0-1 mg daily may be used in younger patients. The dose should be increased by increments until th...

In a preceding communication' we presented electron paramagnetic resonance (EPR) evidence for the existence of labile free radical forms of catecholamine hormones and adrenochrome following rapid oxido-reductions with inorganic reagents in vitro. Although the relevance of these demonstrations to the primary physiochemical interactions of hormones in vivo was left open, generalization of the fin...

The in vitro swelling action of L-thyroxine on rat liver mitochondria as examined photometrically represents an acceleration of a process which the mitochondria are already inherently capable of undergoing spontaneously, as indicated by the identical kinetic characteristics and the extent of thyroxine-induced and spontaneous swelling, the nearly identical pH dependence, and the fact that sucros...

Standard therapy for patients with hypothyroidism is replacement with synthetic thyroxine (T4). However, thyroxine plus triiodothyronine (T3) replacement therapy resulted in marked improvements in several items of the Profile of Mood States and in a few indices of psychometric function and quality of life. The adequacy of thyroxine alone versus thyroxine plus triiodothyronine to treat hypothyro...

Thyroxine has been shown to accelerate the synthesis of carbamyl phosphate synthetase in the liver of Rana catesbdana. Stimulation of carbamyl phosphate synthetase synthesis by thyroxine appears to be relatively specific because of the following observations: (I) succinoxidase activity decreased during the time that carbamyl phosphate synthetase increased; (2) liver catalase responded more slow...